Automated shuttle sorter for conveyors

ABSTRACT

A conveyor sorter includes a shuttle moving transversely to the conveyor direction to place in the path of articles either a pass-through conveyor or a diverting conveyor. The shuttle is mounted on a reversible belt drive and preferably has two diverting conveyors, one on either side of the pass-through conveyor. Multiple shuttles can be installed in series along the main conveyor to allow sorting to many destinations. Large packages can be sorted at high speed, and the shuttle can be replaced easily to reduce down time when repairs are needed.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and is a divisional application ofU.S. patent application Ser. No. 08/905,895, filed Aug. 4, 1997, nowissued as U.S. Pat. No. 5,984,078, issued Nov. 16, 1999.

TECHNICAL FIELD

The present invention relates to a conveyor sorter for divertingarticles, such as parcels, off a conveyor into destination locations,and more particularly relates to such a conveyor sorter includingdiverter stations for diverting parcels at high speed to either side ofthe conveyor, or passing the articles straight through withoutdiversion.

BACKGROUND ART

Package delivery companies pick up millions of packages daily fromthousands of locations over a large geographical area and transportthem, primarily by truck and airplane, to a correspondingly large numberof scattered destinations. To meet a rigorous schedule and provideaccurate deliveries, a package delivery company must use automatedtransfer systems to match incoming packages with proper outgoingtransport headed for the packages' destinations. Because deliveries aretime sensitive, the sorting equipment must be very fast, yet providegentle and accurate handling of packages.

Meeting this goal is particularly difficult in the case of large orheavy packages. Some package delivery companies severely restrict themaximum size of packages they will accept for delivery, but UnitedParcel Service, the assignee of the present application, accepts a widerange of package sizes, shapes and weights.

Belt and roller conveyor systems have often been used in package sortingsystems to move packages from incoming loading docks to outgoingtransport. An initial sorting of packages traveling along a conveyor maybe accomplished by diverting packages from the conveyor based on theirdestinations, or based on their size or another characteristic.

To automate handling of articles in conveyor systems, conveyor diverterassemblies of various types have been developed. Roller bed divertersusing right angle transfer belts are shown in U.S. Pat. No. 4,798,275 toLeemkuil et. al., and U.S. Pat. No. 4,174,774 to Bourgeois. Thesesystems have a relatively large number of moving parts, and repair wouldbe expected to be complex and time consuming.

U.S. Pat. No. 3,926,298, provides a main conveyor having multiplepowered wheels, and a diagonal belt conveyor fitted between the wheelsbelow the normal conveyor surface. A section of the drive rollers can belowered to drop a parcel onto the belt conveyor, without interruptingthe speed of articles moving along the primary path. However, the beltconveyor can divert in only one direction.

U.S. Pat. No. 5,547,084 shows a luggage sorting system in which bags arefed onto a moving carriage that includes multiple conveyors. Afterloading, the carriage moves along a track until it aligns with outputconveyors. Then the carriage conveyors shift the bags from the carriageto appropriate output conveyors. This is not a high speed sorting systembecause the bags must come to rest on the carriage and be transportedlaterally, and then accelerated again after sorting.

Thus, there is a need in the art for a diverter that can reliably divertlarge packages from a main conveyor path, using a non-complex mechanismthat is modular and easy to repair, all while operating at a high speedof throughput along the main path.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved conveyor sortingsystem capable of operating at high conveyor speed and selectivelycarrying large articles to the side of a main conveyor or straightthrough the diverting location.

In accordance with the invention, this object is accomplished byproviding a system and method for transferring articles moving along aconveyor, including a diverter positioned across the longitudinal axisof the conveyor, the diverter including a transport mechanism; and ashuttle mounted on the transport mechanism, the shuttle including apass-through element and a diverting element positioned on one side ofthe pass-through element, the transport mechanism being operative tomove the shuttle between a home position in which the pass-throughelement receives articles from the conveyor and transfers them along thedirection of the longitudinal axis, and a diverting position in whichthe diverting element receives articles from the conveyor and transfersthem away from the direction of the longitudinal axis.

In a preferred embodiment, the system includes means for acquiringdestination information pertaining to the articles; and a controllerselectively operative to operate the transport mechanism in response tothe destination information. An optical reader may be positioned to readsuch destination information printed on a label on the articles. Thetransport mechanism preferably comprises a reversible belt drive onwhich the shuttle is mounted. The pass-through element may be apass-through belt conveyor mounted on a frame carried by the reversiblebelt of the transport mechanism. The diverting element may be adiverting belt conveyor connected at one end thereof to the frame andextending away from the pass-through conveyor. Preferably, a stationarychute is positioned to receive articles from the diverting conveyor, anda free end of the diverting conveyor spaced apart from the frame movesrelative to the stationary chute as the shuttle moves. In thealternative, the diverting element may be a chute, roller conveyor, orother appropriate conveying device rather than the preferred beltconveyor.

In the preferred embodiment, a second diverting element is positioned onthe opposite side of the pass-through element. Thus, the transportmechanism can move the shuttle to position either diverting element inthe path of oncoming articles and divert them to either side of the mainconveyor path.

Multiple diverters may be utilized along the same main conveyor, eitherintermittently or one after the other.

The present invention also provides a method of transferring articles,comprising the steps of conveying the articles along a conveyor in thedirection of a longitudinal axis of the conveyor; and moving a shuttletransverse to the longitudinal axis of the conveyor to placealternatively in the path of the conveyor either a pass-through elementor a diverting element positioned on one side of the pass-throughelement; the pass-through element receiving articles from the conveyorand transferring them along the direction of the longitudinal axis, andthe diverting element receiving articles from the conveyor andtransferring them away from the direction of the longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top plan view of a diverter station embodying the presentinvention.

FIG. 2 shows a top plan view of the diverter station of FIG. 1, with oneof the diverter belts shifted into position to receive an article.

FIG. 3 is a side elevation view of the diverter station of FIG. 1.

FIG. 4 is a side elevation view of the diverter station of FIG. 1 with adiverter belt shifted to the position shown in FIG. 2.

FIG. 5 is a diagrammatic plan view of a sorting system incorporating aplurality of diverter stations embodying the present invention.

FIG. 6 is a partial pictorial view of the diverter station of FIG. 1,with parts removed to show interior detail.

FIG. 7 is a detail view of an apron and dolly assembly for supportingthe free ends of the diverter conveyors of the diverter station of FIG.1.

FIG. 8 is a diagrammatic plan view of an alternate embodiment of adiverter station in which a chute is the diverter element.

FIG. 9 is a block diagram of a control circuit for operating thediverter stations of a sorting system as shown in FIGS. 1-7.

DETAILED DESCRIPTION

Referring now in more detail to the drawings, in which like numeralsrefer to like parts throughout the several views, FIG. 1 shows adiverter station 10 embodying the present invention. One or morediverter stations 10 may be incorporated in a conveyor sorter 1 as shownin FIG. 5, between sections of a linear main conveyor 12 supported on aconveyor bed 13. The main conveyor moves objects, such as parcels P, inthe direction of arrows A. Each diverter station 10 receives parcels Pfrom a conveyor section 12 a of the conveyor 12, and discharges theparcel in one of three directions, namely, to the left (as viewed in thedrawings) onto a left output chute 14 a, to the right onto a rightoutput chute 14 b, or straight through to a downstream section 12 b ofthe conveyor 12. It will be understood that one or both of the outputdestinations 14 a and 14 b may be conveyors, receptacles, or the like,rather than chutes. Also, the present invention can be used with manydifferent types of main conveyors, such as belt conveyors and poweredroller conveyors.

The diverter stations 10 each include a shuttle 15 that movestransversely to the direction A of the main conveyor 12 in a mannerdescribed below. The shuttle 15 has three parcel moving elements, apass-through conveyor 16, a left diverting conveyor 18 mounted adjacentto the left side of the pass-through conveyor 16 and extending out overthe left output chute 14 a, and a right diverting conveyor 20 mountedadjacent to the right side of the pass-through conveyor 16 and extendingout over the right output chute 14 b. The pass-through conveyor 16 isessentially another section of the main conveyor 12, but is mounted onthe shuttle 15 so that it can be moved out of alignment with theconveyor 12. The conveyor 16 preferably is a belt conveyor powered by aconventional motorized pulley (not shown), although another type ofconveyor, such as a powered roller bed, could be used for thepass-through conveyor 16.

The three conveyor elements 16, 18, and 20 of the shuttle 15 are mountedon a carrier 25 that is in turn mounted on a transport mechanism 30,shown in FIGS. 3 and 6. The transport mechanism 30 includes a timingbelt 32 fitted around a pair of notched pulleys 33, one of which isdriven by a reversible servo motor 34 by way of a drive belt 35. Aplurality of spaced apart support idler rollers 36 are positionedbeneath the upper run of the timing belt 32.

The carrier 25 includes an elongate post 40 fixed to the timing belt 32.As best shown in FIG. 6, an H-shaped horizontal frame 42 is attached tothe top of the post 40. The frame 42 defines, spaced in slightly fromthe four extending ends of the “H”, four upstanding roller supports 44for the pulleys of the pass-through conveyor 16. At the extending endsof the “H”, four upstanding roller supports 45 are defined for thepulleys of the two diverter conveyors 18 and 20. The diverter conveyor18 is shown in FIG. 6 with its inner pulley 47 rotatably mounted on apair of the roller supports 45.

The extending end of each of the diverter conveyors 18 and 20 is fittedwith a dolly/apron assembly 48 as shown in FIG. 7 to allow the conveyors18 and 20 to move freely over the output chutes 14 as the shuttle 15moves. The assembly 48 includes a pair of dolly brackets 49 rotatablyattached to the shafts of the conveyor pulley 47. The brackets 49 areconnected by an apron plate 50 which spans the gap between the end ofthe conveyor 18 or 20 and the chute 14 a or 14 b. Each bracket 49extends downwardly to support a wheel 51, so that the end of theconveyor rolls easily along the chute. The apron 50 self-adjusts itsorientation by pivoting about the axis of the pulley 47.

The stepper motor 34 may be operated to move the timing belt 32 ineither direction from a central position as shown in FIGS. 1 and 3. Whenthe shuttle 15 is in the central position, a parcel P traveling alongthe main conveyor section 12 a will be drawn onto the pass-throughconveyor 16 and discharged onto the downstream conveyor section 12 b.However, if the motor 34 is operated to carry the shuttle into theleft-shifted position shown in FIGS. 2 and 4, the diverter converterconveyor 20 is disposed in the path of the parcel P. When the parcel isdeposited onto the conveyor 20, it is carried by the motion of theconveyor 20 over the apron 50 onto the right output chute 14 b. Theshuttle 15 may be moved into a right-shifted position (not shown), inwhich in a similar manner, the parcel will be deposited onto thediverter conveyor 18 and carried to the left output chute 14 a.

In each of the output chutes, 14 a and 14 b, an exit confirmationphotocell 52 is positioned adjacent to where parcels leave the diverterconveyors 18 and 20. The photocells 52 are retro-reflective photocellsthat provide a signal when a parcel passes over the photocells.Additional triangular beam photocells 54 are positioned astride theinput conveyor section 12 a just upstream of the entrance to thediverter station 10, to provide a signal indicating a parcel is enteringthe diverter station. Optionally, additional photocells (not shown)could be positioned just downstream of the diverter stations 10 toprovide a signal when parcels exit the diverter stations onto the outputend 12 b of the following section of the conveyor 12.

As shown in FIG. 5, a sorting system 1 may be constructed by inserting aplurality of diverter stations 10 a, 10 b, 10 c between main conveyorsections 12 a, 12 b, 12 c, and 12 d. In FIG. 5, the diverter station 10a is shown in the central position with the pass-through conveyor 16 alocated to transfer parcels straight on without diversion. The diverterstation 10 b is shown positioned to divert a parcel to the right ontothe diverter conveyor 20 b, and then onto an output chute 114 b. Thediverter station 10 c is shown positioned to divert a parcel to the leftonto a diverter conveyor 18 c, and then onto an output chute 214 a.While three diverter stations 10 are shown in FIG. 5, it should beunderstood that any number of diverter stations can be included in asorting system 1.

Referring to the block diagram of FIG. 9, the operation of the diverterstation 10 is automated through the use of a digital controller, such asa programmable logic controller 60 (PLC), or a general purpose computer,typically having an appropriate microprocessor. The PLC 60 may receiveinput signals from an optical reader 62 that reads barcode ortwo-dimensional symbols (such as MaxiCode symbols) on labels on theparcels P. Such a symbol may contain address information which allowsthe PLC to determine, in a well known manner, which output chute is thecorrect chute at which to discharge the parcel. The PLC 60 may alsoreceive information about the parcel directly from sensors 64, such as ascale or a device for measuring the dimensions of the parcel. A set ofrotary belt encoders 56 are positioned to measure the displacement ofeach section of the conveyor 12, and the output of these encoders isinput to the PLC 60. Parcel information also may be manually entered ata keyboard 65. The PLC 60, in response to these input signals, sendscontrol signals to each of the diverter stations individually, tooperate the motors 34 which move the timing belts, the carriers 25, andconveyor elements 16, 18 and 20.

In operation of a sorter system 1 incorporating a plurality of diverterstations 10, parcels P are placed on the conveyor 12. The PLC receivesinput from the rotary belt encoders 56 associated with the conveyor 12,and from the optical reader 62 or an alternative label reader or manualinput device. The optical reader or other input device is used toacquire destination data about each package as the package is placedonto the sorting system. Any bar codes or other symbols on a parcel aredetected and decoded. Destination information may be embedded in a densecode, or may be stored in a database location the address of which iscontained in a bar code. Furthermore, textual address information on theparcel label can be analyzed using OCR techniques.

It should be understood that the present invention can utilize a feedmechanism, or the parcels can be placed manually onto the conveyor 12.

When a package is imaged at the reader 62, the current count of thefirst encoder 56 is obtained. The rotary encoder device 56 allows thePLC to track how far the section of the conveyor 12 has traveled sinceany particular package was input onto that section. Furthermore, bymonitoring which conveyor section the parcel has reached, the PLC cantrack the location of each parcel as it moves along the conveyor 12 andthrough diverter stations 10. More specifically, the photocells 54inform the PLC when a parcel leaves a conveyor section 12 a-d and entersa diverter station 10. If the parcel is not scheduled for discharge fromthat station, the PLC can add the time required for traversing adiverter station to the encoder count and resume monitoring with thenext encoder associated with the next conveyor section. Or, a photocell(not shown) can be placed at the entry to the next conveyor section tomonitor the entry of the parcel.

A suitable optical reader system for imaging labels is shown in U.S.Pat. Nos. 5,291,564; 5,308,960; 5,327,171; and 5,430,282 which areincorporated herein by reference. Systems for locating and decoding barcodes and the MaxiCode dense code symbology are described in U.S. Pat.Nos. 4,874,936; 4,896,029; 5,438,188; 5,412,196; 5,412,197; 5,343,028;5,352,878; 5,404,003; 5,384,451 and PCT Publication No. WO 95/34043.

A record for each package stored in the PLC memory may contain theparcel identification, destination address, and package characteristics.A description of the contents of the parcel, its dimensions and weight,or a code indicating the contents are fragile or hazardous or have someother special status, may be stored.

In the initial or default state of the sorting system 1, the diverterstations 10 are set to send parcels straight through without diversion.The motorized pulleys of the conveyors 16, 18, and 20 of each stationpreferably are operated continuously while the system is being used, andare coordinated to run the conveyors at approximately the same speed.The speed of the conveyor 12, may be, for example, about 500 feet perminute (about 150 meters per minute).

Once the destination information for the package is known, the PLC 60looks up in an appropriate part of its memory the proper output chute 14a, 14 b, 114 a, 114 b, 214 a, 214 b, etc., corresponding to thepackage's destination, and the diverter station 10 associated with thatoutput chute, as well as the identity of the conveyor section precedingthat diverter station. Preferably, this information is stored in fieldsof the record already created for the package.

In a known manner, the PLC 60 determines when a parcel is approaching adiverter station 10 at which the parcel should be discharged. The PLCreads the encoder counts and photocell 54 signals as the parcel travels,and compares this position information to the discharge locationinformation stored in memory. When the PLC receives signals indicatingthat the parcel has reached a conveyor section immediately preceding thediverter station 10 from which the parcel should be discharged, the PLCsends control signals to the stepper motor 34 of that station. It willbe understood that the PLC need only store three positions of thestepper motor 34 corresponding to alignment of the three conveyors 16,18 and 20 with the main conveyor 12. If the parcel must go to the leftoutput chute 14 a, then the PLC causes the shuttle 15 to be shifted tothe right so that the diverter conveyor 18 is in the path of the parcel.The conveyor 18 then carries the parcel away from the main conveyor anddischarges it onto the output chute 14 a. Similarly, if the parcel mustgo to the right output chute 14 b, then the PLC causes the shuttle to beshifted to the left until the diverter conveyor 20 is aligned with themain conveyor 12, and the parcel is discharged onto the output chute 14b. After the stepper motor 34 receives a command signal from the PLC,the state of the motor 34 may be retained until a change is needed.

In a preferred embodiment, the entire shuttle 15, including thetransport mechanism 30, the carrier 25, and the conveyors 16, 18 and 20,are mounted on a movable base (not shown). In the case of a breakdown,sections of the output chutes 14 can be removed without tools, thedisabled diverter station 10 can be rolled out of position, and areplacement diverter station 10 can be moved into line, all withouttools. This modular construction greatly reduces down time for repairsand therefore increases the productivity of the sorting system 1.

Those skilled in the art will understand that the programs, processes,methods, etc. described herein are not related or limited to anyparticular computer or apparatus. Rather, various types of generalpurpose machines may be used with programs constructed in accordancewith the teachings described herein. Similarly, it may proveadvantageous to construct specialized apparatus to perform the methodsteps described herein by way of dedicated computer systems withhard-wired logic or programs stored in nonvolatile memory, such as readonly memory

In an alternative embodiment, shown diagrammatically in FIG. 8, thediverter conveyors 18 and 20 are replaced by inclined diverter chutes70, one of which is shown. Preferably, an arcuate guide fence 72 ispositioned at the inward end of the chute 70 to change the direction ofa parcel P entering the chute 70 from a main conveyor section 12.Parcels P slide from the diverter chute 70 onto one of the output chutes14.

In another alternative embodiment, not shown, the diverter stations maybe positioned adjacent to one another without intervening conveyor beltsections. In this embodiment, the parcels move directly from onediverter station to the next until they are discharged, and thephotocells 54 are positioned at the boundary between diverter stations.

From the foregoing, those skilled in the art will understand that thepresent invention provides a diverter for a conveyor sorting system thatcan directly and forcefully drive a parcel diagonally to either side ofa main conveyor path, or pass the parcel straight through the diverterlocation, all while operating at a high speed of throughput along themain path. This is accomplished by providing two diverters interleavedor superimposed in the same space, and providing diverting forces towardopposite sides of the conveyor. These diverters can be cycled to providea net motion straight through the diverter, or operated individually todivert parcels off a selected side of the conveyor.

While this invention has been described in detail with particularreference to a preferred embodiment thereof, it will be understood thatmodifications and variations may be made without departing from thescope of the invention as defined in the appended claims.

What is claimed is:
 1. A method for sorting articles, comprising thesteps of: conveying said articles along a conveyor in the direction of alongitudinal axis of said conveyor; and moving a shuttle transverse tothe longitudinal axis of said conveyor to place alternatively in thepath of said conveyor either a pass-through element or a divertingelement positioned on one side of said pass-through element; saidpass-through element receiving articles from said conveyor andtransferring them along the direction of said longitudinal axis, andsaid diverting element receiving articles from said conveyor andtransferring them away from the direction of said longitudinal axis. 2.The method of claim 1, further comprising the steps of: acquiringdestination information pertaining to said articles; and operating saidshuttle in response to said destination information.
 3. The method ofclaim 2, wherein said step of acquiring destination informationcomprises imaging and decoding a label on said articles.
 4. The methodof claim 1, further comprising the step of receiving articles from saiddiverting element in a stationary chute, a free end of said divertingelement spaced apart from said pass-through element moving relative tosaid stationary chute as said shuttle moves.
 5. The method of claim 4,wherein said diverting element comprises a diverting belt conveyor. 6.The method of claim 4, wherein said diverting element comprises a chute.7. The method of claim 1, further comprising the step of alternatelymoving said shuttle to place a second diverting element positioned on anopposite side of said pass-through element in the path of said conveyor.